Aircraft cabin air-supply plant



y 8, 1 54 F. P. STANTON 2,678,542

-AIRCRAFT CABIN AIR-SUPPLY PLANT Filed Dec. 19, 1950 Patented May 18, 1954 r orrice 2,678,542 I AIRCRAFT CABIN AIR-SUPPLY PLANT Francis Patrick Stanton, Bristol, England, assignor to The Bristol Aeroplane Company Limited, Bristol, England, a British company Application December 19, 1950, Serial No. 201,533

Claims priority, application Great Britain December 23, 1949 8 Claims.

This invention relates to cabin air supply plants for aircraft of the kind in which air is delivered by a main compressor to the cabin through a refrigerator unit comprising a cooler of the heat-exchanger type. Such plants usually incorporate a separate cooler (the primary cooler) of the heat-exchanger type, the air delivered from the main compressor to the cabin being cooled in said cooler before passing through the refrigerator unit.

The main object of this invention is to provide a plant of the kind set forth in which a single cooler may be used as a primary and refrigerator cooler with consequent saving in weight and re duction in the bulk of the plant. More specifically, the invention provides that the refrigerator cooler be selectively used either as a primary cooler or as a refrigerator cooler.

Broadly this invention provides that the refrigerator cooler be connected with the main compressor and with the cabin so that air delivered to the cabin from the compressor may pass through only the cooler of the refrigerator unit when the degree of cooling required can be met in this way.

, According to the present invention an air supply plant of the kind set forth is characterised in that air going from the main compressor to the cabin is controlled to pass through the refrigerator unit including itscooler or through the cooler only of said unit.

According to a feature of the present invention the refrigerator unit comprises a compressor, a cooler which receives air from the compressor and a turbine into which the air from the cooler is delivered, the turbine driving the compressor, and there is an air duct from the main compressor to the refrigerator cooler which by-passes the refrigerator compressor, an air duct from the refrigerator cooler to the cabin which bypasses said turbine and a separate valve in each by-pass duct, said valves being controlled so that they are opened and closed together.

According to another feature of this invention ram air is the cooling medium of the refrigerator cooler and there is a cooler control valve which is operative to regulate the flow of cooling medium through said cooler when the bypass valves are open.

According to yet another feature of this invention there is a duct to by-pass the refrigerator unit and convey air from the maincompressor to the cabin, a refrigeratorcontrol valve in said duct and means for adjusting said valve when the by passvalves are closed. M

Customarily, ram air is directed through the primary and refrigerator coolers during flight, as the cooling medium. However, when the aircraft is standing on the ground this is not possible and in hot weather (particularly in tropical countries) the cabin rapidly becomes uncomfortable. To minimise this the pressurising apparatus, including the refrigerator unit, has previously been run to supply cool air for cabin ventilation, a fan being used to circulate air through the refrigerator cooler. Another object of this invention is to eliminate the fan thereby considerably reducing the space requirements and weight ofthe plant and also reducing mechanical complication.

According to this feature of the invention cooling air is drawn through the refrigerator cooler into an engine of the aircraft and used therein for purposes of combustion. Preferably the engine is a gas-turbine engine and the refrigerator cooler is connected to the intake of a compressor of the engine.

The single figure of the accompanying drawing shows diagrammatically, partly in block diagram form, a cabin pressurising and air conditioning plant embodying the invention.

An aircraft cabin l is supplied with air through a non-return valve 2 by a plant arranged in the wing of the aircraft, the air passing along distribution ducting 3, possibly with the addition of recirculated air, to various parts of the cabin as required, and then being returned to the atmosphere at least partly through a discharge valve 4 which is controlled by a pressure sensitive device 5 of known kind which permits the pressure in the cabin to be maintained at a desired value or varied according to a desired law in relation to changes of altitude of the aircraft.

The air supply plant comprises a compressor 6 driven from an engine I of the aircraft through a variable speed gear 8, shown as a two speed gear, though a greater number of speeds may be provided if necessitated by the design and operational characteristics of the plant. The variable speed gear comprises an actuator 9 for selecting neutral or engaged and an actuator II] for selecting low speed or high speed. These actuators may for example be solenoids operating control valves to admit fluid under pressure to hydraulically operated clutches to carry out the required gear changes. The actuator 9 is connected through a switch I l for starting and stopping the plant to a main supply at 12, while the actuator I0 is connected through the plant switch I and a speed control switch [3 to the main supply at l2. The speed control switch I3 is operated by an evacuated capsule I l responsive to atmospheric pressure, the arrangement being such that at low altitudes the variable speed gear is maintained in the low speed setting, and that when a predetermined altitude is reached a change is made into a higher speed. In the case of a two speed drive for a plant designated to operate up to altitudes of the order of 40,000 feet above sea level the change may be made for example at an altitude of about 22,000 feet.

The quantity of air passing through the cornpressor 5 is controlled by a flow control device i l acting upon a throttle valve E5 in the compressor intake duct it in response tovariations in the delivery pressure and in the pressure drop in the throat of a venturi ii in the outlet duct iii. A flow control system suitable for this purpose is described in the British Patent No. 686,547;

The compressor 5 draws air from an opening i9 in the leading. edge. of the wingthrough one pass of a heater 2i of the heat-exchanger type, the. other pass being connected by. a duct 22 to an outlet 2.3 froma jacket 24 which surrounds the engine 3 and is supplied with air under ram pressure through an opening 25. in the leading edge of thawing. The air entering theopening25 isv heated in. its passage over the exterior of the engine I and, according to the setting of avalve 2d, hereinafter referred to as the heater controlvalve, is Wholly or partly directed into the duct 22 or allowed to escape through an outlet. 21; The heated air passing through, the duct 22 and the. heat exchanger 2% in turn heats the air passing through the cornpressorfi into the cabin.

The plantalso comprisesa cooler 28 of the heat-exchanger type through one pass of which cooling air underram pressure inay flow, from a duot2e extending from an opening ii) in the leading edge of the wing, when-valve flaps 30-, hereinafter referred to as the cooler control valve, are, opened. For convenience and clarity in the drawing, the openings i9 and it have beenshown as separate openings, but they are preferably parts of a single opening, the heater and coole matrixes beingsuperposed.

A duct 3! branching from thecoolhrgairduct 29 is'conneoted to the combustion air intake duct 32 of the engine 1, shown as a gas turbine, downstream of control valve flaps 33 and is itself provided witha control valve 34. The valves 33 and 34- are interconnected so that as one-opens the other closes,.the operation being by means which will be more fully described; suffioe itto say. for the moment thatby closing-the cooler control valve 30' and opening the valve 34, the

suction of the engine l -may be used todraw cooling air through the cooler 23 ina direction reverse to the normal direction and thus providecoolingwhen there is no ram pressure cooling air supply, as for example when the aircraft isstationary on the ground.

The second pass of the cooler heat exchanger 28' is connected on the one hand by a duct 35 with the outlet duct i8-of the compressor, and on the other hand by a duct 36 with the cabin I by wayof a Water separator 3i, silencer 38 and the non-return valve 2. Thevvater separator is provided with a Icy-pass 3t containing a control valve it operated by an-actuator ll under the control of ahumidistat lemme cabin.

The ducts 35 and 36 to and from the cooler contain valves 43 and M respectively, hereinafter termed cooler, transfer valves. and there is .anbye pass duct 45, it round each of these valves containing respectively a refrigerator compressor 41 and a refrigerator turbine expander 48, the impellers of these machines being interconnected in known manner by a shaft 49 so that the energy taken out by the turbineexpander is used in the compressorto raise the pressure and temperature of the air so that more heat may be extracted from it in its passage through the cooler.

When the transfer valves 43 and 4d are closed,

it will beunderstood that air from the main compressor 0 flows. in succession through the first part of the duct 35, the refrigerator compressor All, the cooler 28, the refrigerator turbine expandertll,thesecond part of the duct 36 and thus to the cabin. On the other hand, when the transfer valves are open the main bulk of the air takes the path of lesser resistance through the cooler 28, the compressor and turbine parts of the refrigerator being rendered inactive. When the refrigerator as a whole-isin operation maximum efficiency is obtained by keeping the cooler control valve 38 wide open and controlling. the temperature of the air entering the cabin by passing a greater or'lesser proportion of it through the refrigerator. This is achieved by the. provision of a direct flow'duct tr e'containing'a refrigerator control valve 5!. Whenhowever the transfer valves 43 and l are opened so that the cooler is used without the refrigerator compressorand turbine, it is desired that temperature control shallbe by 'means: of the cooler control valve 3!]. The whole of'the airflow is therefore caused to flow throughthe cooler by closing a valve 52 in the direct flow duct 50, this valve conveniently beingcoupled with the transfer valve-44 so that one closes as the other opens.

The temperature control system comprises a variable datum thermostat 53 in the cabin ar'- ranged tosendcontrol signals for increasing or decreasing the temperature to a reversible electric motor 54 rotating a camshaft 55- by means of reduction gearing 56; The camshaft carries a cooler control cam 5 a' refrigerator control cam 58 and a heater control cam 59 operatively connected respectivelywith the'cooler control valve 30, the refrigerator control valve 5!- and the heater control valve 2 5. The camshaft also operates-an electric switch fifidiagrammati cally represented as a pair of brushesadapted to be electricallyconnected'by a conducting segment Eli on a rotating drum.- The closingof this switch energisesan actuator 65 to open the transfervalve lt anol an actuator 62 to open the transfer valve 4 5 and 7 close the direct flow valve 52. The actuators GI and 62 are also connected to the circuit of the actuator liiof-the variable speed gear so-that when the speed control'switch I3 is closed..- say all'filbililldSSfibOVB ZZOOQ feet, and high speed is selected, the transfer valves 43 and are opened and the direct flow valve 52 is closed; The refrigerator is therefore prevented frornworking.

The drawing showsthe control system and valves in a. setting corresponding to nearly full heating power, that is to say the cam 59- is hold ing the heater control valve 26 nearly in its max imum heating position, the cam 51 is holding the cooler control valvetdfully closed, the-switch V Bills closed so-that thetransfer valves 43" and are. open and the direct-flow valvefiZ- is-closed, and the cam 58 i is holdingtherefrigerator-"con trol vvalve 5l :open; which however--has noeffect since the valve 52 in the -same duct is-closed.

over the camshaft turning angle corresponding to the range of movement of the heater control valve 26, so that. the valves 5| and 30 remain open and closed respectively, and no cooling takes place in the cooler 28. l .If the demand for a reduction of temperature has not been met by the time the valve 26 is moved fully to its no heating position, the camshaft continues to rotate, the heater cam 59 enters .aconstant radius range, the refrigerator cam 58 continues in its constant radius range, while the cooler cam 51 enters a decreasing radius range such that the cooler control valve 30 gradually opens, permitting cooling air to flow through the cooler 28 and thus cool the air passing into the cabin.

Should the thermostat 53 call for a greater reduction of temperature than the cooler can produce, rotation of the camshaft past the position in which the cooler control valve 30 is fully open breaks the contact between the brushes of the switch 60 and brings the refrigerator cam 58 to the beginning of its active range. The transfer valves 43 and 44 are therefore closed and the direct flow valve 52 opened, with the result that part of the air from the compressor passes direct to the cabin along the duct 50 while the remainder flows to the cabin by way of the duct 35, refrigerator compressor 41, cooler 28, and refrigerator turbine 48. The air passing through the refrigerator is cooled thereby, while that passing through the duct 50 remains hot from its compression in the compressor '6, and these quantities are matched by suitable dimensioning of the duct 50 so that the net result is that the mixed airflow passing into thecabin has the same temperature as immediately before the commencement of operation of the refrigerator. Further rotation of the camshaft then causes gradual closing of the refrigerator control valve 5| by the cam 58, while the remaining cams and the switch 60 are inactive. As the valve 5| closes, a greater proportion of the output of the compressor 6 passes through the refrigerator to be cooled and a lesser proportion passes directly along the duct 50 with its temperature unchanged. The result therefore is that the temperature of the mixed airflow passing into the cabin is gradually. reduced. Preferably the cams are so shaped that when the camshaft is rotated there is a substantially linear relationship between air temperature at entry to the cabin and the camshaft position (ambient conditions and compressor speed being assumed constant).

Under refrigerating conditions it may be that the relative humidity of the cooled air will rise above 100%, that is to say that liquid water will be present in the airstream. If the relative humidity of the cabin is not objectionably high (it will be lower than that of the air supplied owing to the higher cabin temperature) the water separator 31 will not be brought into action and the water particles will re-evaporate when the air supplied mixes with the hotter cabin air. Further cooling then occurs at this point by the absorption of latent heat of evaporation. If however the humidity of the cabin rises above a predetermined level the humidistat 42 energise the actuator M to move the separator control valve 40 towards its closed position. Part of the airstream is thus caused to flow through the water separator 31 so that its liquid water content is reduced. 5

In an alternative arrangement the direct flow duct 50 may join the duct 36 between the water separator and the silencer so that the refrigerated airstream can be passed through the separator before being warmed by air flowing through the duct 50. i

To allow the cooler 28 or the refrigerator as a whole to be used when the aircraft is standing on the ground, a switch 63 is provided in the cabin whereby an actuator 64 may be energised to open the valve 34 and close the flaps 33 in the combustion air intake duct. lhe actuator 64 also overrides the cooler control cam 51, for example by lifting the cam follower, and closes the cooler control valve 30. The engine suction is thus enabled to draw substantial quantities of cooling air through the cooler 28 in the reverse direction to the normal flow under ram air pressure. This arrangement overcomes the known disadvantages of conventional plants in which cooling air is forced through the refrigerator cooler by a mechanically driven fan.

When using the plant to ventilate the cabin while the aeroplane is on the-ground the cabin air is heated during compression in. the main compressor. In conditions in which the ambient temperature is not too high the cabin air will be sufficiently cooled in passing through only the cooler 28, there being then no call to use the refrigerator compressor and turbine. In this way economy of use is obtained since it is not necessary, as in certain previous plants, to operate the whole refrigerator unit.

Refrigeration is also not required above an altitude of about 17,000 feet and a switch may if desired be provided for manually or automatically energising the transfer valve actuator BI,

.62 at this altitude, or, as shown in the drawing the actuators may be linked to an altitude controlled variable-speed gear system so that the refrigerator is cut out when the plant is operating at altitudes not requiring refrigeration.

In certain circumstances, and when space and weight conditions allow an additional primary cooler may be placed at the outlet from the main compressor, the arrangement being such that under all cooling conditions the cabin air may be passed through both coolers.

I claim:

1. A cabin air supply plant for aircraft having a. main compressor comprising a refrigerator unit comprising a cooler, a compressor and a turbine, an air inlet duct from the main compressor and having a branch leading to said compressor and a branch lay-passing said compressor and leading to said cooler, an air outlet duct from said cooler and having a branch leading to said refrigerator turbine and a branch by-passing said refrigerator turbine, a separate valve in each by-pass branch, means for opening and closing said valves together, an air conduit from said compressor to said cooler, and air conduit means connecting said air outlet duct branch by-passing said refrigerator turbine, and the outlet of said turbine to the cabin.

2. A cabin air supply plant as claimed in claim 1 characterized by the fact that a direct flow acre-pas ducttlcommunicatesr with said: air 1 inlet: duct, by passes said: refrigerator unit and communicates witlrthe cabin, that a refrigerator control valve is;provided in said'direct'fiow duct, and that adjusting. means are: provided for adjusting said refrigerator. control valve when, the Icy-pass valvesare. closed.

3. A cabin air supply plant as claimed in claim Zvcharacterized by the factthat a second" valve issp'ositioned in. said direct fiow' duct, and that control means. are: provided forclosing said by pass" valves; when said. second valve is opened and for-"opening said by-rpass'valves'when said second valve is closed.

4..A cabinair supply. plant for. aircraft havinggamain compressor and an engine comprising a; refrigerator unit comprising a cooler, acornpressor and a turbine, an air inlet duct from the: main compressor and having a brancl1.lead-- ing to-said compressor and having a branch by passing said compressor and leading to said cooler, an airoutlet duct from saidcooler and having. a branch leading to .said refrigerator turbine and a branch by-passing said refrigerator turbine, a'separate valve in each by-pass branch, means-for opening, and closing said: valves together, an air conduit from said compressor to said; cooler; air conduit means connecting said air. outlet duct branch by-passing said refrig erator turbine, and the outlet of said turbine to thegcabin, said cooler having a cooling. air pass, acooling air duct communicating with said cooling; air pass and with the engine for dravring cooling air through said cooler and into the engine for purposes of. combustion when the engine is operating,

5. A cabin air supply plant as claimed in claim 4-: characterized by the fact that conduit means are provided for supplying'ram air to said cooling; air. pass, that a cooler control valve is pro vided for regulating the flow of ram air to said cooling air pass, that means are provided for adjusting said cooler control valvewhen the bypassvalves arev open, that said cooling air duct connects the intake of the engine with said 0001- ing; airpass downstream of, the cooler control valve, that a, valve is positioned iirsaid. cooling air; duct, and that means are interconnected with saidcoolercontrol valve and said cooling air duct. valve for overriding said cooler control valve:

adjusting means so that asonel of these valves opens the other. closes.

6. Acabin air supply plant as clai-medin claim 5,..characterizedby the fact that: a ram: air intake, leads to the engine intake, that a valve is positioned in said ram air intake, and that means are interconnected with the ram air intake valve and the cooling air duct valve, whereby when one. of these valves opens'theother closes.

'7. Acabinair supply plant foraircraft having a main compressor comprising a refrigerator unit, comprising, a cooler, a compressor" and a. turbine, an air inlet duct from the main;com.- pressor and having a branch leading to said:

compressor and abranch lay-passing said compressorand. leading to said cooler, an air outlet duct from said cooler and having a branch leadingto, said refrigerator turbine and abranchuby unit. and communicating with the cabin, a: re-

frigeratcr control valve in said direct flow duct; means for adjusting said refrigerator control valve when the by-pass valves are closed, a secondi refrigeratorvalve. in said direct flow duct,. means for closing said by-pass'valves when said second refrigerator valve is opened andfor opening said by-pass valves when said second refrig erator valve is closed; aid valve actuatingmeans comprising a. reversible electric motor, a cam shaft drivenby said motor, a cam each on said cam shaft for one of said refrigerator valves and said coolercontrol valve, cam followers for said camsand operatively'connected to said one refrigerator valve and said cooler valve, an elec tric actuator having a circuit and operatively connected to one of said by-passvalves, a second electric actuator having a circuit and operatively connected to the other of' said icy-pass valves and to the second refrigerator control valve,

switch means connected in saidactuator circuits and operated by said cam shaft, and a variable.- datum thermostat in the cabinfor transmitting signals to said motor.

3. A cabin air supply plant forv aircraft; having a main compressor comprising a refrigerator. unit comprising a cooler, a compressor anda turbine, an air inlet duct fromthe main. compressor and having a branch. leading to said. compressor and a branch lay-passing said compressor and. leading to said cooler, an. air outlet duct from said cooler and having a branch.lead-. ing to said refrigerator turbine and a branch by passing said refrigerator turbine, a separate valve in each by-pass-branch, means for openingv and closing said'valves together, an. air conduit from said compressor to said cooler; air conduit means connecting'said air outlet duct branchibypassing said refrigerator turbine and the outlet of said turbine to'the cabin, conduit means for I supp-lying a coolant to said cooler, a cooler con: trol-valve for regulating the flow of said coolant to said cooler, means for fully opening said cooler control valvewhen the by-passvalves are closed: and operable for operating the cooler control valve only when said by-pass valves are opened;

References Cited in the file of this patent.

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